1. DALTON AND ATOMIC THEORY
Roots are in ancient philosophy; data is required to
develop basic chemical laws
John Dalton
Elements are composed of tiny particles called atoms
Atoms are indestructible; they re-arrange but never break apart
Atoms of the same element are all the same
Atoms of different elements are different
When atoms combine to form compounds , they do so in simple, whole-numbered ratios (1:1, 1:2, 2:3 …)

2. ATOMIC BOOKKEEPING Atoms consist of protons, neutrons & electrons
All atoms are neutral: have equal #’s of protons & electrons
Mass Number = protons + neutrons
Notation:
AZX X = Element; A = Mass #, Z = Atomic #
Number of protons in nucleus is what distinguishes one element from another

3. ATOMIC STRUCTURE
What Do You Notice About the Structure of the Atom?

4. ATOMIC MASSES From Dalton
All elements have constant atomic masses in compounds
Ratio of elements & ratio of mass of one element to another are always the same
Don’t know actual masses, but ratios are always the same
So why do different forms of some elements have different masses (H, deuterium & tritium?)
Isotopes
Atoms of same element w/slightly different masses
All elements have 2 or more isotopes
What does this do to Dalton’s Theory??

5. ELECTROMAGNETIC SPECTRUM
Protons ID atom; e’s define chemical properties
Electromagnetic energy travels through matter like waves

6. ELECTROMAGNETIC SPECTRUM
C =  x ; 3 x 108 m/sec

7. THE WAVE NATURE OF LIGHT
Maxwell (1873) proposed that visible light was composed of electromagnetic waves
These waves had 2 components that travel
perpendicularly
Electrical
Magnetic
Maxwell’s theory shows how light energy can travel through space

8. PLANCK & THE ELECTROMAGNETIC SPECTRUM
Electromagnetic radiation is emitted in discrete packets called quanta
E = h x 
Each quanta or photon has the same frequency, 
Energy is always emitted in fixed, whole-numbered intervals of h. Why should this be so??

9. EINSTEIN AND THE PHOTOELECTRIC EFFECT
When metal surfaces are exposed to light of a minimum frequency (threshold frequency), electrons are emitted
The energy of those electrons is not proportional to the intensity of light
Photoelectric Effect: A beam of light is really a stream of particles.

10. SO, WHERE ARE WE?
Einstein explained the photoelectric effect w/light as a particle
But the particle theory of light is inconsistent with the notion of light as a wave
For some experiments, light seems to behave as a particle; others as a wave. What to do??

11. ATOMIC LINE SPECTRA
The electromagnetic spectrum is a continuous spectrum
However, separate lines can be observed

12. ATOMIC LINE SPECTRA If you look at the gas discharge for any element,
what you see is a series of sharp, distinct lines
The ’s of the lines are always the same for the
same element, but different for different elements

13. ATOMIC SPECTRA
When elements are heated, they emit discrete bands of color
Each element has its own distinct pattern
When H is heated, it always emits the same color bands
Explanation: e’s are limited only to certain energy levels

14. BOHR ATOM H is the simplest element and has the simplest spectrum
It has lines in both the visible & UV
Balmer: formula able to calculate all observed H ’s
Rydberg: formula to calculate all H ’s

15. BOHR ATOM e’s are like planets circling the sun
e’s move in fixed paths (orbits) each w/a defined energy level
E = -b/n2
Ground State: Lowest energy level
H absorbs energy, e’s jump from one energy level to a higher one
H loses energy, e’s go from higher to lower energy level, and release energy as emitted light

16. BOHR ATOM

17. THE ANSWER: WAVE MECHANICS
Wave Mechanics = Quantum Mechanics
Schrodinger 1st scientist to use quantum mechanics to explain atomic structure
All materials have particles & wave characteristics
de Broglie
 = h / m x 
Energy of any object is related to its mass
Mass , ; small atomic particles have short, measurable ’s

18. WAVE MECHANICS If you create nodes, you change the energy
Waves are divided into equal segments
Orbitals come in different sizes & shapes
Only specific energy transitions can occur

19. WAVE (QUANTUM) MECHANICS
Schrodinger used math to describe the
motion of subatomic particles, much like
Newton did for much larger objects
This math specified where electrons are
most likely to be found in an atom
Since electron waves are 3 dimensional,
one needs 3 quantum numbers to fully
describe them

20. ORBITALS & QUANTUM NUMBERS
Principal Quantum Number (n)
Determines size, shape and position of shell (e wave)
All e’s with same n are said to be in the same shell
Angular Momentum (Secondary) Quantum Number (l)
Divides shells into subshells
n=1 1 subshell s
n=2 2 subshells s,p
n=3 3 subshells s,p,d
n=4 4 subshells s,p,d,f

21. ORBITALS & QUANTUM NUMBERS
Magnetic Quantum Number (ml)
Divides subshells further into orbitals
s: 1 orbital
p: 3 orbitals
d: 5 orbitals
f: 7 orbitals
Heirarchy
Shells (n; 1, 2, 3, …)
Subshells (l; 0 → n - 1)
Orbitals (ml; 2 l + 1)

22. ORBITALS & QUANTUM NUMBERS

23. ELECTRON SPIN
Any moving charged particle, such as an e, creates a magnetic field
Electrons can spin clockwise & counterclockwise, creating opposing spins that allow e’s to be paired
Pauli Exclusion Principle: No 2 e’s can have the same quantum numbers
Spin Quantum Number: ms allows 2 e’s/orbital
Paramagnetic: atom have unpaired e’s; ,magnetic
Diamagnetic: no unpaired e’s; non-magnetic

24. ORBITAL SHAPES Now think of e’s as particles
Heisenberg Uncertainty Principle: Can’t simultaneously predict position & speed of a particle
Since exact e position can’t be predicted, think in terms of e clouds
Also think of probability density as spots on a dart board
Orbitals s p d

25. ORBITAL SHAPES: s ORBITALS

26. ORBITAL SHAPES: p ORBITALS

27. ORBITAL SHAPES: d ORBITALS

28. ORBITAL ENERGIES: ORDER OF FILLING

29. ELECTRONIC STRUCTURE OF ATOMS
Nomenclature
Orbital Diagrams
Aufbau Principle: Build e structure from lowest to highest energy levels
Hund’s Rule: When energy levels are equal, e’s prefer to spread out evenly
Order of e Filling: 1s2, 2s2 2p6, 3s2 3p6, 4s2 3d10 4p6, 5s2 4d10 5p6

30. ELECTRONIC STRUCTURE OF ATOMS
Groups & electronic structure
Electronic structure & recurring properties
Noble Gas Abbreviations: 10:[Ne], 18[Ar], 36[Kr]
Valence Shell
Exceptions to the Rules Cr Cu
e’s prefer symmetrical distribution

31. ELECTRONIC STRUCTURE OF ATOMS & THE PERIODIC TABLE

32. ELECTRONIC STRUCTURE OF ATOMS & THE PERIODIC TABLE

33. ELECTRONIC STRUCTURE OF ATOMS & THE PERIODIC TABLE